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Aug. 28, 1928.

B. D. WILLIS IULTI- DFFISE TELEPHONE SYSTEM w ma. man Nw Sw.

. Bernard :H1/M115 d fin-.-

Patented Aug. 28, 1928.

UNI TE-D S TA TES PATENT -fofF'F-lcs.

BERNARD D. VJILLIS,.OF OAK PARK, ILLNOIS, ASSIGNOR, BY `MESNE ASSIGNMENTS,

TO AUTOMATICELEGTRC INC., OF CHCAGO, ILLINOIS, A,CORPORATION.OF DELA- WARE MULTIOFFICE TELEPHONE SYSTEM.

Application filed September 24, 1923, Serial No. 664 374. Renewed 111151.23, 1927.

The present invention relates to multioice telephone systems in general, but is concerned .more particularly with multi-oftice telephoneA systems in which calls are completed through the medium of automatic switches, and the. principal object is the provision oit new and improved trunking arrangements for such automatic telephone lsystems of the above type as employ socalled universal switchers.

;This case may be considered yan improvement on the co-pending application of Smith, Serial No. 550,451, rfiled April 7, 1922, and issued April 5, 1927, as Patent No. 1,623,320. In the Smith case, the utility for the universal switcher is set forth very completely and, although the universal switcher lis adapted `to be used in any one of a great `number ot situations encountered in large multi-cnice telephone systems, it has been chosen to illus-- trate the present invention in connection with one of the simplercases of multi-otlice telephone systems in which there are not more than tenmainy oiiices and in which one ormore ot the main oflices may have associated therewith one or more fsub-ofiices.

It has been common practicetor some time to provide sub-oices, or satellites, for the lmain eiiices, and to handle `all oi the calls outgoing from a sub-,oiiice through switches in `the associated main office, as well as all the calls incoming to the sub-office, the subotfice containing only the switching equipment required for completing` calls incoming from the mainoliice; for extending calls to the main otlice; and tor completing local calls.

Since it is always desirable in connection with one systemto arrange the trunking system in such a manner that the number of any one line is the same regardless of from which point it is called, it is desirable that a lirst selector in the main oice be seized and made ready for use when the receiver is removed at the calling station in the branch office. Accordingly, the aforesaid irst selector in the main Office isoperated when the first digit is called and as the number is dialled the connection set up step by step in the main oiiice.

Unless special trunking arrangements were madeto prevent it, a call from one subexehange subscriber to another.subscriber 1 l iS inthe `same sub-exchange would take up a trunkl to the main office and would take another trunk trom the main otlice back to the sub-office, thus tying up two inter-oilice trunks needlessly. Accordingly, the long established practice has been to provide arrangements for cutting` out the inter-exchange trunks when the call is local to the originating sub-office, and, in order tov accomplish this result, various trunking layouts have been proposed. For example, Ain the Smith case hereinbefore referred to, a universal switcher is` seized when the receiver is removed,l and a secondary switch associated with `the universal switcher immediately thereupon seizes atrunk extendingto the main exchange, and, if the call is completed through the main exchange, no furthei` trunking operations take place inthe sub-exchange. 0n the other hand, if the call is found to be local to the originating sub-exchange, a second ,secondary switch "is connected up by the universal switcher; the one which seized the main exchange trunk is disconnected; and the ,call iscompleted through the local switches.

Since the trunks with which the universal Switchers are associated are used not only for callsto main but .also for local calls, it is very evident that the number `of these trunks, in practically every case, is greater than the number of trunks extending from the sub-exchange to the vmain exchange. Accordingly, it is ,an object of the present invention to reduce the number ot universalI Switchers required by associating the universal Switchers with the trunksextending from the sub to the main exchange, instead of with the much larger group of trunks through which both main exchange ,calls and local sub-exchange calls are handled.

There are various 4other objects, having to do with the circuit detailsnecessary to carryA out the invention, `which will notfbe mentioned here but willbeexplained .fully hereinafter. i l

In addition to the `Smith application referred hereinbefore, this application in certainrespects may be considered an improvenient on the pending. applicationof Lomax, Serial No. 565.727.filed June V3, 1922.

Reterringnow tothe accompanying single ligure of dra-wine, ene ysubstation denoted by tbereterilmce character. islshenjln.' he

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associated line comprises conductors 11 and 12 terminates at the sub-exchange in the line switch C. rIhis line switch has access to a number of trunks ot which the trunk comprising conductors 31 to 34, inclusive, is one. This trunk has associated with it two secondary switches SS and SS. rl`he secondary switch SS has access to trunks leading to the main exchange, while the secondary switch SS has access only to local trunks leading to selectors such as E.

There is a universal switcher, such as the universal switcher US, associated with each of the repeaters, such as the repeater R, one of which is provided tor each of the trunks extending from the sub-exchange to the main exchange.

The remaining switches in the sub-exchange, as well as all the switches in the main exchange, have been eliminated trom the drawings in order that the showing may be simpliiied.

It is thought that the invention can best be understood from a detailed description of the operation of the apparatus involved. For this purpose it will be assumed that the subscriber at substation A desires to call another subscriber, whose number is 522,689 and whose line therefore terminates in the local sub-oliice, it being assumed that all numbers beginning with 522 are local to the sub-office.

lWhen the receiver is removed at substation A, line relay 15 energizes over line conductors 11 and 12 and closes a circuit i'or the lower winding of switching relay 14 and steppingmagnet 16 in series at armature 21, and at armature 22 connects test wiper 24 to the junction of the lower winding of switching relay 14 and stepping magnet 16.

The further operation depends upon whether the trunk upon which the wipers of the line switch C are standing is busy or idle. It it is busy, the lower winding ot switching relay 14 is short circuited by the ground potential encountered on test Contact 28 by test wiper 24, and the wipers are advanced step by step in search ot an idle trunk by the buzzer-like action of stepping magnet- 16 which is operated through test wiper 24. In this case, however, it will be assumed that the trunk isidle when the call is made, in which case the lower winding of switching relay 14 is not shortcircuited, and said relay energizes immediately. Stepping magnet 16 does not energize at this time on account of the high resistance oi the lower winding of switching relay 14. Upon energizing, switching relay 14 disconnects test wiper 24 from the junction of its own winding and that of stepping magnet 16 and connects it to the private normal conductor 18 at armature 18, thereby preparing the holding circuit; places ground on test contact 29 through test wiper 25 at armature 19; and at armature 17 and 20 disconnects line conductors 11 and 12 from the line relay 15 and ground and extentie them by way of wipers 23 and 26, bank contacts 27 and 30, and trunk conductors 31 and 34 to armatures 48 and 51 of switching relay of the secondary switch SS. As a result ol the ground potential being placed on bank Contact 29, a circuit is closed through the normally closed contacts cont-rolled by armature 44 of relay 41, and the normally closed cont-acts controlled by armature of relay 45, for line relay 46 of the secondary switch Line relay 46 accordingly energizes and places ground on conductor 32 at armature 52, thereby closing the holding circuit for the upper winding of switching relay 14, through contact 28, wiper 24, and armaturc 18 and its working contact, before the slow acting line relay 15 has had time to deenergize.

As a further result of the energization of line relay 46, it closes a circuit for switching relay 45 and stepping magnet 47 in series at armature 53, and at armature 54 connects test wiper 56 to the junction of the winding of switching relay 45 and stepping magnet 47, thereby closing the test circuit. The secondary switch SS operates to select an idle trunk in the manner described tor the line switch S. Assuming that the trunk comprising conductors 61- 63, inclusive, and terminating in bank contacts 58-60, inclusive, is idle, the wipers ot the switch are not moved and switching relay 45 energizes immediately, thereby switching the connection through to the said trunk. Specifically, the energization of' relay 45 results in the test circuit 'being opened and a subsequent holding circuit tor switching relayk14 of the line switch C being prepared at armature 49. Relay 45 also locks itsel'l` to the grounded conductor at. armature 50 and disconnects the slow act-ing line relay 46 therefrom, and at armatures 48 and 51 extends the trunk conductors 81 and 34 through wipers 55 and 57, bank contacts 58 and 60, trunk conductors 61 and 68. and the normally closed contacts controlled by armatures 71 and 72 to the windings of line relay 68 oi the repeater R. Line relay 68 thereupon energizes over the calling line and closes a circuit for release `relay 69 at armature 74. Release relay 69, upon energizing, places ground on the locking conductor 96 at armature 76; opens at armature 77 a point in the circuit ot release magnet 88 of the universal switcher US and. prepares a circuit for the slow acting relay 70, as well as for the stepping magnet et the universal switcher US; and at armature 78 places ground on release trunk conductor 62, thereby completing a new holding circuit for the upper winding ot switching relay 14 ot the line switch C before the slow lll?) lla lift.

arming relay 4601i fthe secondary `switch has had time te .deenergize As further result .of `.the above men.- tioned energization of line relayx68, it vcloses a bridge across vtrunk.conductors X97 and' `98 of the .trunk extending -to the main exchange at armature 7 5. This bridge includes impedance '73, the upper winding Aof the electrofpolarized relay 167, and the resting contact .of armature 79 and said armature. Then this bridge is kclosed the selector in which the trunk terminates at the main eX- change is prepared for operation in the usual manner. It `will be noted ythat the current is now flowing through both the upper and the lower windings of the .electro-polarized relay I67. This relay is not operatively energized at this time, however,

owing -to the fact that the current flowing in.

one winding is i-n opposition to the current flowing in the other winding.

The above operations have occurred in response to the removal of the receiver at the calling substation A, and the universal switcher US as well as the selector associated with the "repeater R and located in the Ina-in exchange are now in readiness to be operated. i f

' hen the calling device at the calling substation is manipulated in accordance with the first digit' 5 of the desired number, the circuit of line relay 68 of the repeater R is opened five times momentarily. Each time line relay 68 deenergizes in response to one of these interruptions, it opens the bridge across trunk conductors 97 and 98 at armature 75 and at armature 74. completes the circuit of relay 70 through armature 77 and its working contact, Relay 70 energizes in response to the first closure of its circuit and, being slow acting, maintains its armature attracted throughout the series of operations. Relay 70 disconnects conductor 97 from the upper talking condenser and connects it directly to the working contact of armature at armature 79. This is the usual expedient made use of to improve the switch control circuitduring diallin s a further result of each .of .the deenergizations of line relay 68, a circuit is .closed in multiple with the slow acting relayv 70 for stepping magnet of the universal switcher US, the circuit at the beginning of the first impulse delivered to magnet 85 bef ing as follows: from ground by way of ar.- mature-74 and its resting Contact, armature 77 and its working contact, off normal contacts 91, slow acting relayA 87, and stepping magnet 85 tobattery. By the'operation of stepping magnet 85 the wiper 84 is advanced step by step a-nd comes intovengagement n with the fifth associated bank contact. Re-

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lay 87 is energized in series with stepping magnet 85 upon the lfirst ef the above men that of stepping magnet 85 closed after the off normal contacts 91 have opened as they do upon the first step of the wiper 84.

At the end of the stepping movement, series relay 87 deenergizes and places ground on t-he winding of relay 86 thereby closing a circuit through the said relay as follows: from ground by way of the resting contact and armature 97, relay 86, normally closed contacts controlled by armature 88, wiper 84, the fifth associated bank contact, normallyclosed contacts controlled by armature 95, and the upper winding of the two` step relay 80 to battery. Relays 8O and 86 energize in series over this` cr-k cuit. However, owing to the copper slug which `is placed on the armature end of the core of relay 86, as isdenoted by the .upper black portion of the core of this relay, Iinstead of the more usual position at theheel end of the. core, the said relay7 86 is slightly slow in energizing and accordingly relay 8O is able to energize first. Relay 80, on the other hand, is a two step relay and pulls up only part yway when .energized through itsA ill) upper winding, which is composed of. a

small number of turns'of wire having a relatively high resistance. When relay 8O is energized through this upper winding, its contacts marked l close, while the ones marked 2 remain unoperated. Accordingly, armature 95 is brought into engagement lun with its associated contact andthe lower armature of the relay is brought into engagement with its'associated contact. A rmature 95, it may be stated, does not perform any useful function at this time from a circuit standpoint, but is provided to aid the. lower armature spring in bringing thel armature proper of the relay to a. stop so that it will not complete its stroke.. The lower armature of relay 80, upon coming into engagement with its associated contact, closes a locking circuit through the lower winding of the relay. This locking circuit is not effective at this time, however, owingl to the fact that the lower winding is practically short circuited by the ground potential applied to the junction of the two windings through the low wound relay S6. It will be seen from the above that since relay 8O is a twostep relay and has not yet pulled all the way up, there is no danger of the circuit through the wiper Sli being opened before armature 88 of relay `86 can be operated, otherwise relay 80. might energize too quickly and open the circuit of relay 86 before the latter could operate to close a locking circuit for itself.

`When armature 88 of .relay 86 comesinle lili) l it:

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engagement with its associated contact it closes a circuit through off normal contacts, 90 for release magnet 83 and when armature 88 is attracted still further it disconnects wiper 84;, thereby opening the initial circuit of the upper' winding of relay 80. Then this occurs, the lower winding ot relay 80 is no longer short circuited and becomes energized 'in-series with the upper winding of the relay, whereupon the armature proper ot the relay pulls all the way up resulting in the litt-h bank contact being disconnected at the normally closed contacts controlled by armature 95, andr also in the second bank Contact being connected up at the upper armature oi' the relay, thereby preparing a circuit for relay 81.

Responsive to the closure otv the above mentioned circuit -lor release magnet 83, the

wiper 8d is restored to lnormal position,

whereupon the circuit `of release magnet 83 and relay 86 is opened at oli' normal contacts 90, and the relay and magnet deenergize.

Simultaneously with the above described operation of the universal switcher US, the selector in which the trunk comprising conductors 97 and 98 terminates at the main exchange is operated in the usual manner responsive to the interruptions ot the bridge across the conductors 97 and 98 at armature 7 5. This selector switch raises its wipers to the fifth level and then selects an idle trunk in the usual manner.

Then the calling subscriber operates his calling device in accordance with the second digit 2 in the desirednumber, two interrup- A tions are produced in the outgoing trunk circuit at armature 7 5 of line relay 69, whereupon the selector last seized raises its wipers to the second level and selects an idle trunk. rlhe universal switcher US is again operated in the previously described manner and wiper 84- is brought into engagement with the second associated bank contact. Since the upper armature of relay 80 is operated, two step relay 81 is connected up and operates in the same manner as described for the relay 80; closes its contacts marked 1 when the circuit of its upper winding is closed; and operates its contacts marked 2 when wiper 8d is disconnected by relay 86. The wiper 811 is restored to normal by the release magnet 83 in the usual manner.

It will be noted that, in this case, the upper armature ot relay 81 connects the second bank contact with the upper winding ot relay 82 so as to enable the relay 82 to be energized through the second contact upon the next operation of the universal switcher. Accordingly a second reason :for the use ot a two step relay manifests itself at this time, namely-to prevent the relay 82 Afrom beineconnected up to the second bank con tact f)estore the ground connection is removed from' thewiper 84. Otherwise -relays 81 and 82 might operate one after the other, resulting in the premature operation of relay 82.

Responsive to the ynext opera-tion of the calling device at the substation A, the circuit of linerelay 68 of the repeater R is twice opened, whereupon line relay 68 deenergizestwice and interrupts the circuit across conductors 97 and 98 twice at armature 7 5. In response to each of these inter.- ruptions the selectorto which the connection has been extended in the main exchange raises .its wipers to the second level and selects an idle trunk (not shown) extending back to the originatin@r sub-exchange. Simultaneously, the wiper 84 of the universal switcher US is advanced into engagement with the second associated bank Contact and when relay 87 deenergizes a circuit is completed through relay 86, vwiper 84, and the upper contacts of relays 80 and 81 for the upper winding of relay 82. Accordingly relays 82 and 86 energize in series. Relay 82, upon energizing, Ycloses a locking circuit for itselia at its lower armature, and relay 86, upon energizing, completes the usual circuit for release magnet 83, whereupon wiper 84 is again restored to its normal position. As a further result of the energization of relay 82, it connects the booster battery 93 to the release trunk conductor 62 through the resistance 92 and disconnects direct ground therefrom. The application of the booster battery 93 to the release trunk conductor 62 results in the energization of the marginallyy adjusted relay 41. This relay is also a two step relay and energizes only part way with the booster battery applied to its lower winding in series with the regular exchange battery. I

As a result of the first step of the operation of relay l1, it places ground on conductor 99 at armature 14, thereby closing a circuit through the normally closed contacts controlled by relay 101 for line relay 102 of the secondary switch SS. thereupon energizes, causing the secondary switch SS to select an idle trunk in the usual and well known manner. Assuming that the trunk comprising conductors 113- 115, inclusive, isy idle, the wipers of the switch are not moved and switching relay 101 energizes immediately. Uponenergizing, relay .101 locksitself to conductor 99 and disconnects the line relay 102 at armature 106; opens the test circuit and prepares a circuit for the upper winding of relay 41 at armature 105; and at armatures 1041 and 107 extends the trunk conductors 31 and 341 through wipers 113 andl 115 and armatures 132 and 135 to linerelay 121ot` the selector E. Line relay 121 thereupon energizes over the calling line in multiple with the line re lay 68 of the repeaterfl and closes a circuit for r-f'wlay 1.22 at armature .125.12

Relay 102 .hill

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. and the switches at the main exchange and` l back over the trunk to the sub-exchange to lease relay 122' thereupon energizes and prepares the switch' for operation at armature 128, at the same time placing ground on release trunk conductor'114 at armature 127. The placing of ground' on conductor 114 results in a circuit being closed through wiper 111, armature 105 and its working Contact, release trunk conductor `100, `and armature 431 and its working contact for the upper winding of relay 41. Responsivey to the closure 'of this circui't, relay 41 energizes fully; disconnects its lower winding at the normally closed contacts controlledv by armature 42; connects release trunk conductor 32` with rei lease trunk conductor 10() at the normally open contacts controlled by armature 42 so as to hold up the connection from the se'- le'c'tor E", and at the normal-ly closed contactsv controlled by armature 44 opens the holdingr circuit of relay 45, ,whereupon relay 45 deenergizes and disconnects the associated wipers. This results in the partially set up connection extending' through the repeater R be released in the usual and well known manner.

The connection is now switched over throughlthe secondary switch SS to the local selector E and the said lselector E is in readiness to be operated in accordance with the next digit in the desired subscribers number.

when the subscriber at substation A manipulates his. calling device' in accordance with the next digit 6 of the desired niimber, line relay 121 of. the selector E deenergizes a corresponding number of times. Each time the line relay 121 deener'gizes, it closes a circuit for the` vertical magnet 138 as follows: fromground by way of the rest-` ing contact of armature 134, armature 126 and its resting Contact, armature 128 and its working contact, series relay' 123, and vertical magnet 138 yto battery. By the' operation of vertical magnet 138, the wipers 142-144, inclusive, are raised step by step until they stand opposite the sixth level ofy bank contacts. Relay 123 is energized in series with vertical magnet 138 and, being slow' acting, maintains' its armature attracted throughout'the vertical` movement`.

By the conjoint action of relay 123 and off normal contacts 141, which'close upon thel first vertical step, a circuit is completed through interrupter contacts 14() forv step'- ping relay 124. Relay 124 energizes responsive' to the closure of its circuit and closes'v a locking circuit for itself at armature 130, and a't armature 131 prepares a circuit for rotary magnet 139.

At the end of the vertical movement, slow acting series relay 123 deen'ergizes and'com'- pletesthe rotary magnet circuit at armature 129, whereupon rotary magnet 139 ener# gizes and advances' the wipers into engagement with the' firstl set of bank contacts in the level opposite which` they were raised. Near the endof its stroke, rotary magnet 1'39 opens the circuit of stepping relayl 124, whereupon relay 124 deener-gizes and opens' the circuit of rotary magnet 1:39,' whereupon rotary magnet 139 deenergiz'es also.

'Ihe'y further operation depends upon, whether" the ytrunk terminating in the lirst set of bank contacts is busy' er idle. In' case it is idle, switching relay 125 energizes im-k mediately. Assuming itl to be busy, how ever, switching relay 1 2'5 isvv short circuit'ed by thek groundA potential? encountered on the test contact of the busy trunk by test wiper 143 and does not energize. In this case', stepping rrelay 124 energizesk again, and again' closes the circuit' of rotary magnet 139 at armaturel 131, whereupon the switch wipers are advanced into engageinentI withE thev next set of bank contacts. This alter'- nateoperation of' stepping relay 124` and rotary magnet 139, continuesv until' an idle' trunk iis rea'cli'ech/ which trunk'y may be' assum'ed is the one-` terminating at bank con-A tacts 1454147, inclusive.' Vilhenz this occurs, switching relay 125, being no longer short circuited', energizes in series with stepping relay 124'; disconnects ground* from'. armature-126 of' line relay 121 at armature 134, thereby opening the' circuit of release' relay' 122; opens the test circuit and prepares theA holding circuit at-arm'ature' 133;' and at ar'- matures 132' andl 135" disconnects conductors 113 s114115 from thewindngs of line 'relay 121 and extends thereby' way` of wipers 142' and 1411', bank' contacts' 145 and-'147, the associated trunk conductors to the l'inerelay of the associated connector switch- The line and release4 relays (not shown) ofthis'connectar' switch new' energize" andi the latter' places ground on the associated release' trunk' conductor, vtliereby closing aiho'lding circuit tliF'Ouvgl'i''QSL COll'tlfCt 146,51'11@ tSt W'lpl" 143 for switching relay 125aswe`ll' asffor the upper winding'of relays 41an'd 14 bef'ore'y the slow acting release relay` 122 has had' time to deenergize. y u

Responsive to the two remaining operations ofthe' calling' device a't substation A, the connector switch is operatedin'theusuval lili;

manner to complete thet connection to the `de'- sired'line and, vwhen the" subscriber at sub,- station A hangs up his receiver after'having inished the call,'tl1`e connector switch re'- mo'ves ground from vthe associated release trunk conductor whereupon switching relay of the selector E, re`lay`41'afn`d rela'y' 14' 1 of the line switch C dee'nergize.' Switching l relay 125, upon de'energizingf, completes a circuit for release magnet 136? at armature' The circuitl includes armature 126 and its resting contact, armature 128Qand its resting contact, and ofnorn-i'al contacts 137.

By the operation yof release magnet 136 the wipers of the selector E are restored to normal position, whereupon the circuit of release magnet 136 is opened at off normal contacts 137. V*The connection is now released and the apparatus involved is ready for use in another connection.

Referring now again to the universal Switchers US associated with the repeater R, it is apparent that in case the wiper 84 lands upon an open contact responsive to the dialling of a digit which determines that the call can not be intended for the local sub-A exchange, no circuit is completed for relay 86 and accordingly the release magnet 83 is not at that time operated and the wiper 84 is left standing ofi' normal. vWhen this happens the' steppingmagnet 85 can not be again operated until the connection being established is releasedand the repeaterl R is again seized. This is made possible owing tothe fact that the rst impulse oit current to the magnet 85 must always come through the oli normal contacts 91 which are opened as soon as the wiper 84 leaves its normal position, aft-er which the circuit of stepping magnet is maintained at armature 89 of rela 8 i XWhen a :call isjextended through the repeater R and is not switched through the secondary switch SS to the sub-exchange the universal switcher US is standing oil' normal until the connection is released at which time a circuit is closed through armature 74 and its resting contact of line relay 68, armature 77` and its resting contact of release relay 69, and ofi' normal contacts 90, for release magnet 83, resulting in the release of wiper 84 in the usual manner.

It will be seen from the'foregoing that the present invention provides a very economical arrangement for the switching of calls from one path to another in that the switching devices are associated with the outgoing trunks which are small in number. It will be seen further that the provision of the two step relay in connection with the universal switcher provides a very positive operation.

What is claimed is:

l. In a telephone system, a trunk, a lirst switch and a second switch individual to said trunk, twogroups of trunks accessible to said switches, respectively, means responsive to a call over Isaid trunk Jfor operating said first switch to select a trunk in the associated group, and means for subsequently releasing said firsty switchand for causing said second switch to select an idle trunk in the associated group, the last named means being controlled from the trunk selected by said first switch, said control being exercised or not according to the called' number.

2. In a telephone system. a trunk, two aut' iatic switches individual thereto, two

groups of trunks accessible to said switches, respectively, means responsive to a call over said trunk for operating one of said switches to select a trunk in the associated group, registering means individual to the last named trunk, said registering means being operated over said last named trunk in accordance with the called number, and means controlled by said registering means 'tor releasing the last named one of said switches and tor causing the other of said switches to select an idle trunk in the associated group.

3. In a telephone system, a trunk, an auto- .matic switch associated with said trunk, a group of trunks accessible to said switch, means responsive to a call over aid first named trunk to cause the said switch to select an idle trunk in the associated group, a second automatic switch individual to the irst named trunka switching relay, and means controlled from the trunk seized by the irstnamed switch for energizing said switching relay to release said iirst named switch and to operate the second of said switches to seize an idle trunk in the associated group.

4. In a telephone system, a trunk, an automatic switch associated' with said trunk, a group ot' trunks `accessible to said switch, means responsive to a call over said trunk to cause the saidswitch to select an idle trunk in the associated group, a second automatic switch associated with the iirst named trunk, a switching relay, and means controlled from and individual to the trunk seized by the first named switch for energizing said switching relay to release said iirst named switch and to koperate the second of said switches to seize-an idle trunk in the associated group, said means being effective or not in accordance with the number called.

5. In a telephone system, a trunk line, means lfor extending a connection thereto from a calling line and for subsequent-ly extending said trunk line towards a called line, and means individual to said trunk line and controlled in accordance with the called number for releasing said connection and for connecting the calling and called lines over another path.

6. In a main-exchange and branch-exchange telephone system, a trunk line in the branch exchange, means torjconnecting this trunk line with a calling line, a switch individual to said trunk line, a branclrtomain trunk line extending from a repeater in the branch exchange to a selector in the main exchange, means responsive to the connection of the said branch-exchange trunk line to the calling line for connecting the said branclrexchange trunk line with said branch-to-main trunk line, means in said repeater for repeating the series of impulses representing the called number over the trunk line to the main exchange to operate llo switching means including the selector on the distant end or" vthe branch-to-main trunk line to complete the connection, a registering device in the branch exchange opeiated by contacts in said repeater simultaneous with the repeating of the impulses to the main exchange, a local-connection trunk line, and means controlled by said register in case the number desired is a branch exchange number for disconnecting said branch-exchange trunk line from said branch-to-main trunk line and for connecting it instead to said local trunk line whereby the branch to main trunk line through saidv iii-st mentioned switch is freed for use by other subscribers and the connection is completed over the local trunk line to the desired local subscriber.

7. In an automatic telephone system, an exchange including two automatic. switches, groups ot' trunks leading to different exchanges accessible by way of the iirst of said switches, trunks local to the exchange acces sible by way of the second switch, means for extending a connection to the first switch, and means controlled through a trunk line seized by the first switch and effective if a telephone number local to the exchange is called i'or releasing the first switch and for extending a connection through the second switch.

8. In an automatic telephone system, an exchange including two automatic switches, groups of trunks leading to ditferent exchanges accessible by way of the first of said switches, trunks local to the exchange accessible by way of the second switch, means for extending a connection to the first switch, and means controlled through and individual to the trunks accessible to theA first switch and effective if a telephone number local to the exchange is called for releasing the iirst switch and for extending a connection through the second switch.

9. In an automatic telephone system wherein the establishment of connections is controlled by groups of digit impulses, a trunk terminating in an automatic switch and having a branch terminating in a sec* ond automatic switch, said second switch being normally unresponsive to the seizure ot the trunk, means in said trunk controlled through the :first mentioned automatic switch for rendering the second mentioned automatic switch responsive, groups of trunks accessible to the respective automatic switches, and means in the trunks accessible to the first mentioned automat-ic switch effective if certain groups of the controlling digit impulses are of certain values for controlling said first named means.

10. In a telephone system, a trunk having two branches each terminating in an automatic switch, one of which switches is normally unresponsive to the seizure of thel lto a trunk line in the associated group and for further extending a connection over the connected trunk lines in accordance with certain digits of a desired telephone number, means individual to said last mentioned trunk line operated under predetermined conditions for releasing the established connection, and for rendering the normally unresponsive switch responsive to digit inipulses for extending a connection over the branch of the firsty mentioned trunk that leads to the normally unresponsive switch.

1l. In a telephone system, a trunk have ing two branches each terminating in an automatic switch, 4one of which switches is normally unresponsive to the seizure of the trunk, groups oi' trunks accessible to the respective switches, means for setting up a connection over the other automatic switch to a trunk line in the associated group and i'or further extending a connection over the connected trunk lines in accordance with certain digits of a desired telephone number, means individual to said last mentioned trunk line operated in accordance with certain digits of a desired telephone number for releasing theestablished connection and for rendering the normally unresponsive switch responsive to digit impulses for extending a connection over the branch of the first mentioned trunk that leads to the normally unresponsive switch.

12. In a telephone system, a first automatic switch, a second automatic switch seized thereby, said two switches including talking conductors, a busy test conductor, and an auxiliary conductor, means controlled over the auxiliary conductor for applying a busy potential to the test conductor, means controlled over the talking conductors for releasing the connection between the two switches, and additional means effective under predetermined conditions `for applying an increased potential to the test conductor, for also causing the release vof the said automatic switches.

13. A universal switcher comprising a register responsive to a plurality of digits. and a like plurality of two step relays con nected to the bank contacts of said register.

In witness whereof, I hereunto subscribe` my name this 21st day of September, A. D., 1923.

BERNARD D. WILLIS. 

